Re: Major Havoc help (was: Vectrex on Vector Monitor?)

My contribution to the Vector Fix-it FAQ,,, :')

For Asteroids and Asteroids Deluxe boards with no signs of life:

Unplug the monitor from the harness at it's molex connector to avoid
damage to it - when the monitor sits in spot killer state too long things
can fry!

1. Start out by verifying that the clock is running. (The crystal on these
boards
breaks off WAY too easily.) Then check that the CPU and ROM's are good.
If you found nothing or it's still dead, you've got a watchdog reset
happening - see if pin 40 of the CPU is toggling (it's supposed to be held
high).

2. To figure out who is causing the watchdog resets (the MPU or the VSM
(Vector
State Machine)), take the 74LS42 at L5 (L6 on Asteroids) and socket it,
then
lift out pin 1 to isolate DMAG0.
a) If the board stops resetting, the MPU is not the problem and you should
be
able to play a game "blind" or switch into test mode and listen for any
beeps
indicating RAM/ROM problems. That will at least help you get the MPU side
running properly and then you can play the game blind.
b) A board that is still resetting has a problem with the MPU and also
possibly
the VSM. Check the ROMS, RAM and especially the 74LS245 (or AM83048)
at E2 (E3 on Asteroids). Once you fix the reset problem, switching to test
mode
should reveal any other missed RAM/ROM issues and verify the MPU is
running ok. You should now be able to play the game blind.

3) Place pin 1 of the 74LS42 (DMAG0) back into it's socket. If the
watchdog is
resetting, it's time to look at the VSM side of things. If it's not
resetting, plug
the monitor back into the harness and look for some video.

For the VSM, check the PROM at C8 (C9 on Asteroids) and surrounding state
machine signals for HALT, DMAGO, STOP, GO and the like. The rest is pure
grunt
work to check the state machine is running properly. Someone else please
feel free to add details to the VSM debug procedure...

Paul

Mark Jenison <jenison@cig.mot.com> on 29/10/98 05:16:58 PM

Please respond to vectorlist@mcfeeley.cc.utexas.edu

To: vectorlist@mcfeeley.cc.utexas.edu
cc: (bcc: Paul Tonizzo/SYBASE)
Subject: Re: Major Havoc help (was: Vectrex on Vector Monitor?)

Clay,

I've been keeping this e-mail around as debugging tips, but I realized that
I
have NO IDEA on how to actually do the things you mention. See my
question/comments below...

On Aug 12, 10:56am, Clay Cowgill wrote:
> Subject: RE: Major Havoc help (was: Vectrex on Vector Monitor?)
> > >quit reading it after arguing with some twit for far too long about
> > 6809
> >
> > "twit" huh? Not very nice :)
> >
> :-) *grin* I probably should've put a smiley in there, but I was
> typing fast before a meeting... ;-)
>
> > Speaking of twits, I have a couple MH boards I would like to resurrect
> > from the grave. Board repair is not my specialty, but I have the
> > capabilities to do it. Anybody have some tips/Atari signature guide/
> > anything to help me with this task?
> >
> What kind of problems are they exhibiting? I've had good luck fixing
> vector boards just starting at the crystal and tracing through the game
> with nothing fancier than a logic probe. (A LOT of vector boards are
> "resurrected" just by replacing a dead crystal, IMHO.) Just step
> through it logically:
>
> Is the clock running? (check crystal and clock on microprocessors)

Which pin is the clock on microprocessor, assuming Z-80? assuming 6809?

> Is the board coming out of reset? (check watchdog outputs and reset
> pins)

Which pins are reset pins?

> Does it look like the processor is running? (check datalines and address
> bus for activity)

Which are data lines?

> Is it doing something useful? (see if chip selects on multiple ROMs are
> occuring)

What/where is chip select?

> Is the Vector generator running? (check the signals in the vector
> generator-- "GO, Reset, etc." is it hitting the Vector generator ROM?
> Is the vector generator ASIC good?)

Huh?

> Are the DACs getting input data?
> Are the DACs generating output voltages that make sense?
>
> I find the majority of problems in the clock circuit, followed by the
> vector generator (usually after the DAC outputs), and then the program
> ROMs....

I think this is all good advice in general, but us dummies who don't have
volumes of computer chip books (I don't even have ONE) could use some
herding
in the right direction...

Thanks! (PS. When do Multi-pac's start shipping again? I haven't received
mine yet...).

----------------------------------------------------------------------
Mark Jenison E-mail address: jenison@cig.mot.com
Cellular Infrastructure Group Motorola--Arlington Heights, IL
----------------------------------------------------------------------
Received on Fri Oct 30 08:32:17 1998